Tar sands, also known as oil sands or bituminous sands, are sand deposits impregnated with a dense, viscous petroleum-like material generally termed bitumen. Tar sands are found throughout the world, though the largest known deposits lie in the province of Alberta, Canada, and in Eastern Venezuela, though deposits in the lower continental United States are sizable.
Tar sands have interesting -- and enticing -- properties in that the bitumen can be separated from the sand by a variety of methods, including in situ including thermal, emulsion-steam drive, and even atomic explosion; mining followed by processing of various types such as direct coking, anhydrous solvent extraction, cold water separation, hot water separation, and the like; and any of these followed by possibly various methods of upgrading of the separated bitumen to a more salable product generally described as synthetic crude oil.
Despite the fact that the existence of the tar sand deposits and that the bitumen can be separated have been known for years, nevertheless, as a matter of fact, separating the bitumen on a practical, economical basis has so far pretty much escaped a good solution.
The ruins of various tar sand ventures are legion, generally sunk in the mire of the huge quantity of total material to be handled to try to recover some of the bitumen, and, in a sense, burned out by the overconsumption of fuel to provide heat for the recovery process, which heat all too often has been generally lost out of the process without adequate retention or recycle to make a commercially economically viable process.
The tar sand, or possibly more properly bituminous sand, comprises a mixture of sand, water, and bitumen. The sand component typically is predominantly a quartz wetted with connate water, or oil, or both, and partially filling or surrounding the wetted particles is a film of bitumen in the sand voids. This material has a composition that is variable, but typically contains about 83 weight percent sand, the balance being water and bitumen. There are wide variations in the bitumen content from virtually nothing to upwards of 17 weight percent. Again, the big problem is the huge weight of raw material which must be processed in order to recover the bitumen, compounded by the loss -- or rather consumption -- of bitumen or of the recovered hydrocarbon products in providing heat for the recovery of further bitumen. The situation is compounded by heat losses from such processing system through outflow of heat with product streams and/or spent sand streams.
Needed to have a viable tar sand recovery process is a method that is thermally efficient.